It is known that the efficiency of solar cells can be improved by the elimination of the dead layer at the surface of the solar cell. Eliminating the dead layer improves the response of the solar cell to light in the blue and violet portions of the solar spectrum. The performance of the solar cell in this, i.e., the blue and violet portion of the solar spectrum, is enhanced by providing a junction depth which is on the order of 1000 to 1500 angstroms below the top surface of the silicon semiconductor material. The actual depth of the junction below the top surface of the solar cell varies and will be a function of the thickness of the electrical contact grid and antireflection coating applied on the surface of the silicon.
The shallow junction solar cell, or violet cell as it has been named, exhibits increased performance in the blue and violet regions of the solar spectrum in which the greatest power output of photons from solar radiation are concentrated. However, the violet cell with its shallow junction presents problems during the formation of the surface grid electrode or electrical contact to prevent the electrode from punching through the shallow junction. Methods have been developed for forming a fine finger geometry on a solar cell having a shallow junction. However, the method of forming the contact pattern often requires extensive steps of diffusion, oxidation, photolithography, metallization, and plating. The numerous processing steps, especially photolithography, greatly adds to cost of the solar cell and slows the rate of processing and fabrication of the solar cell.
Thus, it would be highly desirable to have a process of forming an electrical contact to a shallow junction solar cell without punching through the junction.